Single-acting ram with fluid relief means



March 14, 1961 s. E. FARMER 2,974,636 SINGLEACTING RAM WITH FLUID RELIEF MEANS Filed May 10, 1960 Si'CII'l] L/ E. Farmer INVENTOR.

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SINGLE-ACTING RAM wrrn FLUID RELIEF MEANS Stanley E. Farmer, Portland, reg., assignor to Cascade lglanufacturing Co., Portland, 0reg., a corporation of regon Filed May 10, 1960, Ser. No. 28,046

9 Claims. (Cl. Ill-33) This invention relates to rams or fluid motors, and more particularly to a novel construction for a singleacting, fluid-pressure-operated ram having means for bleeding any fluid from the cylinder of the ram that may collect on the nonpressure side of the rams piston.

In a conventional single-acting ram, fluid under pressure is used to move the nams piston from one end of the cylinder for the ram toward the other, during a powered stroke. The usual piston has some form of sealing means about its circumference sealing it to the inner wall of the cylinder, and this is for the purpose of confining pressure fluid introduced into the cylinder to one side of the piston. The usual sealing means, however, never provides an absolutely perfect seal, and after any cycling of the ram fluid leaks to the nonpressure side of the piston.

Fluid collecting on the nonpressure side of a piston will impair the operation of a ram, if means is not provided for exhausting such fluid. One solution is to pro- "vide a port in the end of the cylinder adjacent the location of the piston at the end of its powered stroke. This enables fluid to be expelled from the cylinder by the piston. Such a construction has its disadvantages, however. An open port at the end of a cylinder results in a loss of actuating fluid, and this loss is accompanied by fluid dripping from the ram cylinder, which is messy. A way of preventing loss of fluid is to install a bleed or return conduit connecting the port and the reservoir for the fluid system actuating the ram. Such a bleed conduit, however, introduces other problems.v In the usual conduit there is resistance to fluid flow 'therethrough, and in a ram having a relatively fast moving piston, pressures can be built up on the nonpressure side of the piston tending to cause rupture or other failure of the bleed conduit, its connection with the ram cylinder, or seals on the nonpressure side of the piston. In this connection, it should be remembered that in the usual singleacting ram having a piston rod projecting from the nonpressure side of its piston and out through one end of its cylinder, the piston area on the pressure side of the piston is larger than the piston area on the opposite .side of the piston, and as a result there is a force multiplication that can produce pressures in any fluid on the nonpressure side of the piston considerably larger than the pressure of the fluid used to actuate the tram.

Generally it is an object of this invention to provide :an improved construction for a'single-acting ram that includes a novel bleed system taking care of the herein :above described problems in a highly practical and satisfactory manner. 4 f More Specifically, it is an object of this invention to provide relief means for the nonpressureside of a "piston in a single-acting, fluid-pressure-operatedv ram which comprises a chamber formed in the piston rod of the ram and passage means connecting the chamber to the interior of the ram cylinder whereby fluid collectthe chamber and be collected therein. According to an atent ice - fluid until it can flow out the exhaust conduit means,

thus to eliminate peaks in pressure in the fluid.

Another object of the invention is to provide a novel relief means for a single-acting ram of. the above description wherein the chamber is closed save for its connection with the interior of the ram cylinder, and in operative condition normally at lea-st partially filled with air. Such closed chamber, by reason of the compressible gases contained therein, operates as a form of closed surge chamber and evens out fluctuations in pressure by olfering a path of relatively low resistance for the escape of fluid. The resistance offered to the flow of fluid increases as the chamber fills with fluid as this is accompanied with compression of the air. Thus, automatically, the more fluid that collects on the nonpressure side of the piston, the greater the pressure tending to produce discharge of fluid through the exhaust or relief conduit means. a

A still further object of the invention is to provide a novel construction for a ram that comprises a cylinder, and a piston and piston rod assembly mounted for reciprocation within the cylinder, said assembly comprising a piston head and a tube connected by radially extending hollow pins to the head. The tube functions as the piston rod, and the inside of the tube constitutes a collection chamber connected by the hollow pins to the interior of the cylinder. 4

Other objects and advantages are attained by the invention, which is described hereinbelow in conjunction with the accompanying drawings, wherein:'

Fig. 1 is a side view of a single-acting ram constructed according to an embodiment of this invention, with portions of the ram cylinder, piston and piston rod broken away to illustrate details of construction; and

Fig. 2 is a schematic illustration of a ram as contemplated, and a hydraulic system for the ram, the system including a reservoir, pump and valve mechanism.

Referring now to the drawings, 10 indicates generally a ram constructed according to one form of the invention. The ram in the embodiment illustrated may be used as the hoist cylinder in a fork-lift tractor or truck. In such an application, return of fluid from the nonpressure side of the piston to the reservoir in the hydraulic system for the rain is important, in order to prevent hydraulic fluid from leaking over the cylinder and the .surroundings of the fork-lift truck where it is used. While the ram is described in connection with a fork-lift truck, it should be understood that the ram is not limited to such a specific application, and that the construction of the invention is adapted for any application where fluid leakage to the nonpressure side of the ram piston is a problem.

Describing ram 10, 12 indicates an upright ram cylinder. With the ram used as the hoist cylinder on a fork-lift truck, the cylinder ordinarily is mounted in fixed position on the frame of the truck through a mounting portion 14 welded to the outside of the cylinder.

Mounted within cylinder 12 and reciprocable up and down therein is a piston and piston rod assembly comprising a piston head portion 16 and a rod' portion 18. Upon actuation of the ram, the piston and piston rod portions may move from the position illustrated in Fig. 1 upwardly to a position wherein the rod portion is extended "from the cylinder and piston portion 16 is adjacent the f. ing on the nonpressure side of the 'piston may flow .into

'top of the cylinder.

sembly falls to the base of the cylinder under the force of gravity when fluid is allowed to escape from the bottom end of the cylinder.

Closing off the bottom end of cylinder 12 is an end wall 29. The top cylinder 12 is closed off by a plug 22. In the embodiment illustrated, plug 22, is detachable from the cylinder, to accommodate the mounting of the piston and piston rod assembly within the cylinder. Thus, plug 22 includes a threaded portion 24 that is screwed into an internally threaded portion 26 provided the top of the cylinder. A seal, such as an O ring 28, is provided between the plug and the cylinder. Piston rod portion 18 extends upwardly through an accommodating bore 30 provided the center of plug 22. Adjacent the upper end of the plug is a rubber wipper seal 32, held snugly in contact with the periphery of the rod by a helical garter spring 34.

Connecting with the interior of the cylinder at the bottom end thereof is a supply conduit means 36, for the supply and exhaust of pressure or actuating fluid to the base of the cylinder. In the form of the invention shown, conduit means 36 comprises a hose 38 connected to the cylinder through a fitting 40. Pressure fluid is admitted through hose 38 and fitting 40 against the bottom or pressure side of piston portion 16.

A relief or bleed conduit is provided the top end of the cylinder that connects with the interior of the cylinder on the nonpressure side of the piston. In the embodiment illustrated, the relief conduit comprises a hose 42 connected to the cylinder through a fitting 44.

Considering now the construction of the piston and piston rod assembly 16, 18, piston portion 16 comprises a piston head 50 having an axially extending stem portion 52 of reduced diameter projecting upwardly from the top thereof. At the base of stem portion 52 in Fig. 1 is an annular, radially projecting flange portion 54 (that forms part of the mechanism performing as a piston in the construction). Below flange portion 54 is a mounting portion 56, and an annular element 58 referred to as a piston half fits about mounting portion 56. Element 58 is held from shifting axially by snap rings 60 and flange 54. The inner circumference of annular element 58 is sealed to mounting portion 56 by O ring 62 and back-up ring 64. Sealing the outer circumference of element 58 to the inner wall of the cylinder are chevron rings '66 positioned on the element and adjacent flange 54 by adapters 68, 69.

Rod portion 18 in the embodiment of the invention illustrated comprises a tube 71 with its hollow center closed at its top end by a plug 72 welded to the tube. The bottom of tube 71 fits over stem portion 52 and sits on flange 54. A bore 74 extends diametrically through stem portion 52, and bores 76 are formed in the bottom end of the tube that register with the ends of bore 74. The tube is held in place on stem portion 52 by roll pins 78. Bore 77 connects bore 74 with the inside of tube 71. Roll pins 78 are hollow, and their centers provide a passage means connecting the interior of cylinder 12 with bores 74, 77 and the inside of tube 71. It should be noted that tube 71 has a portion 80 of reduced outer diameter extending from the top of flange 54- (the top side of the mechanism that functions as a piston in the construction) up to and beyond where the roll pins connect the interior of the cylinderwith the interior of tube 71. In this way the passage means connecting the inside of cylinder 12 and the inside of tube 71 is essentially always open.

Fig. 2 illustrates a hydraulic system used in operating the ram. A reservoir 82 is provided for holding actuating fluid. Fluid is pumped from reservoir 82, by a pump 84, through a conduit 86 and valve 88 to hose 38. Valve 88 is a two position valve, and in one position conduit 86 feeds hose 38, and a conduit 90 extending from the valve to the reservoir is closed off. In another position, conduit 86 is closed olf, and hose 38 is connected through valve 88 and conduit 90 with reservoir 82. Hose 42 connects with reservoir 82, and constitutes a self-emptying passage for the flow of fluid from the top of cylinder 12.

Explaining the operation of the device, it will be noted that the chamber within the rod portion is closed save for its connection with the inside of cylinder 12. Normally the chamber is filled with air, which is compressible. Assuming now that fluid has leaked beyond the chevron rings to the top side of the piston portion, at some time during the use of the ram it will be necessary to-extend the rod portion fully from the cylinder, and to do this the piston portion is urged upwardly until it reaches the top of the cylinder. If there is fluid above the piston portion, such fluid will tend to be forced by the piston portion out hose 42 and back to reservoir 82. Ifthe piston portion is shifted rapidly, a large pressure peak in fluid above the piston is prevented, by reason of the fact that as the piston portion nears the top of the cylinder, fluid not only flows through tube 42, but also through the centers of the hollow roll pins and into the chamber within the piston rod 12. These roll pins therefore provide an alternate path for fluid preventing pressure peaks. Since the chamber within the rod portion is closed, fluid flows into the chamber only with compression of air within the chamber. As air within the chamber is compressed, a greater resistance to flow of fluid into the chamber is produced. What in effect is provided is a closed surge chamber, that operates to prevent pressure peaks, and also functions to offer increasing resistance to flow thereinto as fluid accumulates therein.

While there has been described an embodiment of the invention, it is appreciated that changes are possible in the parts and/or their organization. It is desired not to be limited to the .specific embodiment of the invention shown, but to cover all modifications and variations that would be apparent to one skilled in the art, and that come within the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In a single-acting fiuid-pressure-operated ram having a cylinder, and a piston and piston rod mounted within the cylinder, said piston having a pressure side that fluid under pressure acts upon with the piston moving in a powered stroke in one direction within said cylinder and an exhaust side opposite said pressure side, the combination of means for introducing fluid under pressure into said cylinder against the pressure side of said piston, and means for bleeding fluid from the cylinder on the exhaust side of said piston, the latter means comprising a chamber formed within said piston rod, and passage means formed in the piston rod connecting the interior of the cylinder only on said exhaust side of said piston with said chamber.

2. In a single-acting fluid-pressure-operated ram having a cylinder, and a piston and piston rod mounted within the cylinder, said piston having a pressure side that fluid under pressure acts upon with the piston moving in a powered stroke in one direction within said cylinder, the combination of supply conduit means connectnig with the interior of the cylinder on the pressure side of said piston for introducing fluid under pressure against the pressure side of said piston, and means for bleeding fluid from the cylinder on the side of said piston opposite said pressure side, said means comprising relief conduit means connecting with the interior of the cylinder on the side of said piston opposite said pressure side, a chamber formed within the piston rod, and passage means formed in the piston rod connecting the interior of the cylinder only on said opposite side of said piston with said chamber, said relief conduit means providing a self-emptying passage for the flow of fluid, said chamber providing an empty space for storing fluid and operating in conjunction with said relief conduit means and operable temporarily to store any excess fluid until the same can flow through the self-emptying passage of the relief conduit means.

3. In a single-acting fluid-pressure-operated ram having a cylinder, and a piston and rod mounted within the cylinder, said piston having a pressure side that fluid under pressure acts upon with the piston moving in a powered stroke in one direction within said chamber, the combination of supply conduit means connecting with the interior of the cylinder on the pressure side of said piston for introducing fluid under pressure against the pressure side of said piston, and means for bleeding fluid from the cylinder on the side of said piston opposite said pressure side, said means comprising a chamber formed within said piston rod, passage means formed in the piston rod connecting said chamber with the interior of the cylinder only on the side of said piston opposite the pressure side, said chamber being closed save for said passage means and in an operative position for the ram being at least partially filled with air, and relief conduit means connecting with the interior of the cylinder on the side of said piston opposite said pressure side, said relief conduit means providing a self-emptying passage for the flow of fluid, said chamber functioning as a variable pressure surge chamber for temporarily storing fluid and producing a pressure on fluid stored therein through the air in said chamber being compressed when displaced by such fluid.

4. In a single-acting fluid-pressure-operated ram having a cylinder, and a piston and rod mounted Within the cylinder, said piston having a pressure side that fluid under pressure acts upon with the piston moving in a powered stroke in one direction within said chamber, the combination of a reservoir, supply conduit means including a pump connecting the reservoir with the interior of the cylinder on the pressure side of said piston for introducing fluid under pressure against the pressure side of said piston, and means for bleeding fluid from the cylinder on the side of said piston opposite said pressure side,

said means comprising a chamber formed Within said piston rod, passage means formed in the piston rod connecting said chamber with the interior of the cylinder only on the side of said piston opposite the pressure side, said chamber being closed save for said passage means and in operative position for the ram being at least partially filled with air, and relief conduit means connecting the interior of the cylinder on the side of said piston opposite said pressure side with said reservoir, said relief conduit means providing a self-emptying passage for the flow of fluid from the cylinder to said reservoir, said chamber functioning as a variable pressure surge chamber for temporarily storing fluid and producing a pressure on fluid stored therein through the air in said chamber being compressed when displaced by such fluid.

5. A single-acting fluid-pressure-operated ram comprising, in operative position, an upright cylinder, a piston and piston rod mounted within the cylinder, said piston moving from bottom to top ends of the cylinder during a powered stroke, supply conduit means connecting with the bottom end of the cylinder for introducing fluid under pressure against the bottom side of said piston, exhaust conduit means connecting with the top end of the cylinder for bleeding fluid from the cylinder collecting on the top side of the piston, a chamber formed within said rod extending upwardly from said piston, and passage means connecting said chamber with the interior of the cylinder only on the top side of said piston and at a location adjacent the top side of said piston.

6. The ram of claim 5 wherein the chamber within said rod is closed save for said passage means and in operative condition normally filled at least partially with air that is compressed when displaced by fluid partially filling the chamber and when compressed exerts a pressure on such fluid.

7. The ram of claim 5 wherein said rod has a portion of reduced diameter extending from the top side of said piston to where said passage means connects with the interior of said cylinder.

8. A single-acting ram comprising, in operative position, an upright cylinder, a piston head mounted within the cylinder for reciprocation therein and movable from the bottom to the top end of the cylinder during a powered stroke, said piston head having a bottom side that constitutes a pressure side for the piston head that fluid under pressure acts upon during a powered stroke, and a top side that constitutes an exhaust side for the piston head and an axially extending stem portion of reduced diameter projecting upwardly from the top side thereof, an elongated hollow tube mounted with its bottom end on the top side of the piston head and fitted over said stem portion and extending out the top end of the cylinder, said piston head closing oif the bottom end of the tube, at least one radially extending hollow pin projecting through said stem portion and tube and connecting the tube and the piston head, the hollow center of the pin providing a passage placing the interior of the tube with the interior of the cylinder, said tube in fluid connection constituting a piston rod in the ram, means closing of the top end of the tube, passage means for introducing fluid under pressure to the bottom end of the cylinder and against the pressure side of said piston head, and passage means for bleeding fluid from the top end of the cylinder.

9. The ram of claim 8 wherein said tube has a portion of reduced outer diameter extending from the top side of the piston upwardly past the level of said pin.

References Cited in the file of this patent UNITED STATES PATENTS 

